Ultradispersed catalyst compositions and methods of preparation

ABSTRACT

The present invention relates generally to ultradispersed catalyst compositions and methods for preparing such catalysts. In particular, the invention provides catalyst composition of the general formula:
 
B x M y S [(1.1 to 4.6)y+(0.5 to 4)x] 
 
where B is a group VIIIB non-noble metal and M is a group VI B metal and 0.05≦y/x≦15.

PRIORITY

This application is a divisional of U.S. application Ser. No.11/604,131, filed 22 Nov. 2006, now U.S. Pat. No. 7,897,537 which inturn claims the benefit of U.S. provisional patent application60/739,182, filed 23 Nov. 2005.

FIELD OF THE INVENTION

The present invention relates generally to ultradispersed catalystcompositions and methods for preparing such catalysts.

BACKGROUND OF THE INVENTION

The use of catalysts in the processing of hydrocarbons is well known.Catalysts enable hydrocarbon processing reactions, such ashydrotreating, hydrocracking, steam cracking or upgrading reactions, toproceed more efficiently under various reaction conditions with theresult that the overall efficiency and economics of a process areenhanced. Different catalysts are more effective in certain reactionsthan others and, as a result, significant research is conducted into thedesign of catalysts in order to continue to improve the efficiencies ofreactions. Many factors such as catalyst chemistry, particle size,support structure and the reaction chemistry to produce the catalyst arevery important in determining the reaction efficiency and effectivenessas well as the economics of a particular catalyst.

Catalysts can be generally categorized in one of two classes, namelysupported and unsupported catalysts. Supported catalysts are more widelyused due to several advantages including the high surface area availableto anchor active phases (usually metals) predominantly responsible forthe catalytic activity on the support. Supported catalysts may also beadvantaged over unsupported catalysts as no separation of catalysts fromreactants is required from within or outside the reaction vessel.

While effective in many applications, supported catalysts can bedisadvantaged when performing under conditions and with feedstocks thatinevitably produce solid deposits within the porous network of thecatalyst support. In such cases a progressive loss of catalystperformance due to pore plugging occurs, making larger quantities ofcatalysts required for a given process to ensure that the reactionsprogress efficiently.

Unsupported catalysts are not physically supported on a solid matrix;they may be less expensive to produce as no solid support matrix isrequired. In reactions where unsupported catalysts are soluble in thereaction media, they may be disadvantaged by the difficulties ofrecovering them from the products stream which will increase reaction orproduction costs as catalysts must be replaced or, alternativelyrequires that the reactants are subjected to costly separationprocesses. Frequently, unsupported metal based catalysts with equivalentparticle size or diameter than supported catalysts offer lower surfacearea of catalytic active phases. However, unsupported catalysts withparticle size below the micron range are advantaged over supportedcatalysts by increasing the surface area available of active sites forreaction and thus, may enable a reaction to proceed more efficiently ascompared to a reaction utilizing a supported catalyst.

While there is no universal rule with respect to the superiority of oneclass of catalyst over another, in many systems, a primary considerationin choosing or designing a catalyst system is the potential trade-offbetween the reaction efficiency and costs of unsupported catalystsversus supported catalysts.

As a result, there is a continued need for catalyst compositions for usein certain reactions wherein the reaction efficiencies of unsupportedcatalysts are combined with the cost efficiencies of supportedcatalysts.

Furthermore, there has been a need for catalyst compositions in themicro to nanometer size to enhance surface area efficiencies. Ideally,catalyst compositions in this size range should be produced fromrelatively simple chemistry so as to minimize production costs. It isalso an advantage if such unsupported catalyst compositions can bereadily separated from the reaction process so as to enable effectiverecovery and recycling of the catalyst back to the reaction process.

SUMMARY OF THE INVENTION

It is an object of the present invention to obviate or mitigate at leastone disadvantage of conventional catalysts.

In accordance with the invention, there is provided catalystcompositions of the general formula:B_(x)M_(y)S_([(1.1 to 4.6)y+(0.5 to 4)x])

where B is a group VIIIB non-noble metal and M is a group VI B metal and0.05≦y/x≦15. In various embodiments, 0.125≦y/x≦8, 0.2≦y/x≦6 or y/x=3.

In accordance with a further embodiment, the invention provides catalystcompositions of the general formula:B_(x)M1_(y)M2_(z)O_((2 to 3)z)S_([(0.3 to 2)y+(0.5 to 4)x])

where B is a group VIIIB non-noble metal and M1 and M2 are group VI Bmetals and 0.05≦y/x≦15 and 1≦z/x≦14. In various embodiments, 0.2≦y/x≦6and z/x is 10≦z/x≦14 or z/x is 12. In another series of embodiments1≦z/x≦5 or z/x=3.

In various embodiments, the ultradispersed suspension is characterizedby a median particle diameter between 30 nm to 6000 nm or 60 nm to 2500nm.

In a further embodiment, the invention provides a method of preparing abi-metallic ultradispersed catalyst comprising the steps of: preparing afirst precursor solution containing a metal salt of a Group VIII Bmetal; preparing a second precursor solution containing a metal salt ofa Group VI B and a sulphiding agent; admixing the first and secondprecursor solutions with a hydrocarbon feedstock to form separatemicroemulsions; and, admixing the first microemulsion with the secondmicroemulsion to form a bi-metallic microemulsion mixture.

In one embodiment, the bi-metallic microemulsion mixture is subjected toa decomposition process to form an ultradispersed catalyst composition.In other embodiments, the bi-metallic microemulsion mixture isintroduced into a reaction process to form an ultradispersed catalystcomposition within the reaction process.

In a still further embodiment, the invention provides a method ofpreparing a tri-metallic ultradispersed catalyst composition comprisingthe steps of: preparing a first precursor solution containing a metalsalt of a Group VI B metal; preparing second and third precursorsolutions containing a metal salt of a Group VI B metal with asulphiding agent and a Group VIII B metal, respectively; admixing thefirst, second and third precursor solutions with a hydrocarbon feedstockto form separate microemulsions; and, admixing the first, second andthird microemulsions to form a tri-metallic microemulsion mixture.

In one embodiment, the tri-metallic microemulsion mixture is subjectedto a decomposition process to form an ultradispersed catalystcomposition. In other embodiments, the tri-metallic microemulsionmixture is introduced into a reaction process to form an ultradispersedcatalyst composition within the reaction process.

In each embodiment, one or more surfactants may be added to any one or acombination of the precursor solutions.

Other aspects and features of the present invention will become apparentto those ordinarily skilled in the art upon review of the followingdescription of specific embodiments of the invention.

DETAILED DESCRIPTION

Ultradispersed catalyst compositions for use in hydrocarbon reactionprocesses and methods of preparation are described herein.

Catalyst Compositions

In accordance with a first embodiment of the invention, catalystcompositions characterized by their particle size and ability to formmicroemulsions are described. The catalyst compositions are bi- ortri-metallic compositions dissolved in a protic medium containing a VIIIB non-noble metal and at least one VI B metal (preferably one or two) inthe presence of a sulfiding agent. The atomic ratio of the Group VI Bmetal to Group VIII B non-noble metal is from about 15:1 to about 1:15.The catalyst compositions according to the invention can be used in avariety of hydrocarbon catalytic processes to treat a broad range offeeds under wide-ranging reaction conditions such as temperatures from200° C. to 480° C.

More specifically, the invention describes bi-metallic catalysts of thegeneral formula:B_(x)M_(y)S_([(1.1 to 4.6)y+(0.5 to 4)x])

where B is a group VIIIB non-noble metal and M is a group VI B metal and0.05≦y/x≦15.

In more specific embodiments, 0.2≦y/x≦6 and preferably y/x=3.

The invention also provides a second class of catalysts described astri-metallic catalysts of the general formula:B_(x)M1_(y)M2_(z)O_((2 to 3)z)S_([(0.3 to 2)y+(0.5 to 4)x])

where B is a group VIIIB non-noble metal and M1 and M2 are group VI Bmetals and 0.05≦y/x≦15 and 1≦z/x≦14.

In more specific embodiments of the tri-metallic catalysts, the y/xratio is in the range of 0.2<y/x<6. The range z/x is preferablydetermined by the desired use of the catalyst. For example, selectivityto lighter hydrocarbons (C1-C5) will preferably have a z/x of 10<z/x<14and more preferably z/x=12. Alternatively, selectivity to intermediatehydrocarbons for mild hydrocracking (Low cracking functionality) willfavor 1<z/x<5 and preferably z/x=3.

Formula Examples

As examples, if y/x=0.05, y=1 and x=20. Thus, at this y/x ratio,B_(x)M_(y)S_([(1.1 to 4.6)y+(0.5 to 4)x])

would include catalyst compositions ranging from B₂₀MS_(11.1) toB₂₀MS₈₄₆₆.

If y/x=15, y=15 and x=1, at this y/x ratio,B_(x)M_(y)S_([(1.1 to 4.6)y+(0.5 to 4)x])

and would include catalyst compositions ranging from BM₁₅S₁₇ to BM₁₅S₇₃.

Particle Size Characterization

The particle sizes within the microemulsion preferably have a medianparticle diameter between 30 nm to 6000 nm, and more preferably between60 nm to 2500 nm. The sizes, chemical compositions and structures ofsuch particles are verified using known techniques such as dynamic lightscattering (DLS), X-Ray diffraction (XRD), transmission electronmicroscopy (TEM), small angle X-ray diffraction, X-ray photoelectronspectroscopy (XPS) and others.

Constituent Metals

The Group VI B metals include chromium, molybdenum, tungsten andmixtures thereof. The Group VIII B non-noble metals include, iron,cobalt, nickel or mixtures thereof. Preferably, the combinations of themetals are iron, cobalt, nickel or mixtures thereof with chromium,molybdenum, tungsten or mixtures thereof. The suitable Group VI B metalswhich are at least partly in the solid state before contacting theprotic medium, comprise polyanions such as molybdates, tungstates,chromates, dichromate; or oxides such as molybdenum oxides, tungstenoxides, chromium oxides. The suitable Group VIII B non-noble metalscomprise water-soluble metal salts such as acetate, carbonate, chloride,nitrate, actylacetonate, citrate and oxalate.

Process

Active catalyst compositions are formed from catalyst precursorsolutions. The catalyst precursor solutions are combined with ahydrocarbon feedstock for a particular processing reaction underconditions to promote the formation of a microemulsion utilizing thefollowing general methodology.

Bi and Tri-Metallic Catalyst Preparation

Separated or combined metal saturated aqueous precursor solutions areprepared under appropriate conditions (temperature between 20 to 50° C.and 1 atm). In the case of a bi-metallic catalyst, one (for combinedsolutions) or two metal saturated aqueous solutions are prepared whereasfor a tri-metallic catalyst, one, two (for combined solutions) or threemetal saturated aqueous solutions are prepared.

The first precursor solution contains metal salts of Group VI B or VIIIB non-noble metals; the second contains metal salts of Group VI B orGroup VIII B non-noble metals and the third solution contains Group VI Bmetal. For aqueous solutions which contain Group VI B metals, ammoniumsulphide can be admixed under controlled conditions of pH to form thiosalts.

Following preparation of the precursor solutions, each solution isadmixed with a hydrocarbon feedstock under conditions to form one ormore separated microemulsions. Non-ionic surfactant with an HLB(Hydrophilic-Lipophilic balance) between 4 and 14 may be optionallyadded to enhance the microemulsion formation. Other surfactants may alsobe used.

To prepare a bi-metallic catalyst from separate microemulsions, onecontaining metal salts of Group VI B and ammonium sulphide and the othercontaining an VIII B non-noble metal, are mixed.

The bi-metallic microemulsion may be optionally sent through adecomposition process under certain operating conditions (temperaturebetween 150-450° C. and pressure between 1 atm-70 atm, and morepreferably temperature between 225-325° C. and pressure between 14atm-28 atm) to remove the protic medium and to produce theultradispersed catalyst before sending it into the reactor.

To prepare a tri-metallic catalyst from separate microemulsions, threeprecursor microemulsions, one containing metal salts of Group VI B andammonium sulphide, another containing VIII B non-noble metals and thelast one containing metal salts of Group VI B, are mixed.

To prepare a tri-metallic catalyst from two microemulsions; onecontaining two metal salts of Groups VI B and VIII B non-noble metalswith ammonium sulphide and another containing metal salts of Group VI B;are mixed.

The tri-metallic microemulsion is optionally sent through adecomposition process under certain operating conditions (temperaturebetween 150-450° C. and pressure between 1 atm-70 atm, and morepreferably temperature between 225-325° C. and pressure between 14atm-28 atm) to produce the ultradispersed catalyst.

In an alternate embodiment, the precursor solutions are combined beforeadmixing with the hydrocarbon feedstock in order to form a singlemicroemulsion. This method of formation may be applied to both thebi-metallic and tri-metallic catalyst systems.

Catalyst Production and Use

A particular advantage of the invention is the ability to producedifferent catalysts particularly suited to different process.

EXAMPLES

The following examples demonstrate the synthesis and uses of thebi-metallic catalysts from the present invention for various hydrocarbonprocessing applications.

Example 1

Co—Mo(S) bi-metallic catalysts were prepared using the followingprocedure. A first aqueous solution containing 20 wt % ammoniumheptamolybdate (AHM) was mixed with an aqueous solution containing 50 wt% ammonium sulphide at a S:Mo ratio of 4:1 at a temperature of 25° C.and pressure of 1 atm. The resulting solution was mixed with ahydrocarbon stream (Base Oil) containing surfactant Span 80 to stabilizethe formed a microemulsion wherein the hydrocarbon component was 95 wt %of the microemulsion and Mo was 4750 ppm with respect to thehydrocarbon.

A second aqueous solution containing 22.5 wt % of cobalt acetate,Co(OAc)₂ was mixed with a hydrocarbon stream (Base Oil) containingsurfactant Span 80 to stabilize the formed microemulsion wherein thehydrocarbon component was 95 wt % of the second microemulsion and Co was1240 ppm with respect to the hydrocarbon.

These separated emulsions are mixed in a decomposition process at 250°C. and 1 atm in a continuous manner to form the dispersed catalyst. Thecatalyst size obtained measured by dynamic light scattering (DLS) was438 nm.

Example 2

Ni—W(S) bi-metallic catalysts were prepared using the followingprocedure. A solution containing 29.7 wt % ammonium metatungstate (AMT)was mixed with an aqueous solution containing 50 wt % ammonium sulphideat a S:Mo ratio of 2:1 at a temperature of 25° C. and pressure of 1 atm.The resulting solution was mixed with a hydrocarbon stream containing 2%Span 80™ (a surfactant) to form a microemulsion. The hydrocarbon streamwas a vacuum gas oil sample (VGO1) having a composition as shown inTable 1 wherein the hydrocarbon component was 97 wt % of themicroemulsion and W was 4750 ppm with respect to the hydrocarbon.

TABLE 1 % wt Cut (° C.)  0-273 4 273-380 33 380-450 33 450⁺ 30 S 3.36API Gravity 18.6

A second solution containing 15 wt % of nickel acetate, Ni(OAc)₂ wasmixed with a hydrocarbon stream containing Span 80™ and VGO1 to form asecond microemulsion wherein the hydrocarbon component was 94 wt % ofthe second microemulsion and Ni was 1250 ppm with respect to thehydrocarbon.

These separated emulsions were mixed in a processing unit to form thebi-metallic catalyst and perform a hydrotreating reaction underconditions presented in Table 2.

TABLE 2 Reaction Conditions Temperature (° C.) 320 Pressure (MPa) 8 LHSV(h⁻¹) 0.5 (Liquid Hour Space Velocity) H₂ flow (SCCM) 100 (Standardcubic centimeters per minute)

The resulting oil characterization is shown in Table 3 and shows theeffectiveness of the catalyst in removing sulphur, increasing API numberand reducing heavy fraction.

TABLE 3 % wt Cut (° C.)  0-273 6 273-380 36 380-450 34 450+ 24 S 0.5 APIGravity 23

Example 3

Co—Mo(S) bi-metallic catalysts were prepared using the followingprocedure. A first solution containing 22.3 wt % ammonium heptamolybdate(AHM) was mixed with a second solution containing 22 wt % of cobaltacetate, Co(OAc)₂ and the resulting solution were mixed with an aqueoussolution containing 50 wt % ammonium sulphide at a S:Mo ratio 8:1 at atemperature of 25° C. and pressure of 1 atm. The resulting solution wasmixed with a hydrocarbon stream (VGO1) to form a microemulsion whereinthe hydrocarbon component was 95 wt % of the microemulsion with Cocontent 4650 ppm and Mo content 1350 ppm with respect to thehydrocarbon. The reaction conditions were the same as example 2.

The resulting oil characterization is shown in Table 4 and shows theeffectiveness of the catalyst in reducing sulphur content.

TABLE 4 % wt Cut (° C.)  0-273 5 273-380 35 380-450 32 450+ 28 S 0.3 APIGravity 19

Example 4

Ni—W(S)/MoO₃ tri-metallic catalysts were prepared using the followingprocedure. A solution containing 15 wt % ammonium metatungstate (AMT)was mixed with an aqueous solution containing 50 wt % ammonium sulphideat a S:W ratio 5:1 at a temperature of 25° C. and pressure of 1 atm. Theresulting solution was mixed with a hydrocarbon stream (VGO1) containingSpan 80™ to form a microemulsion wherein the hydrocarbon component was95 wt % of the microemulsion and W was 1850 ppm with respect to thehydrocarbon.

A second solution containing 15 wt % of nickel acetate, Ni(OAc)₂ wasmixed with a hydrocarbon stream (VGO1) containing Span 80T″ to form asecond microemulsion wherein the hydrocarbon component was 95 wt % ofthe second microemulsion and Ni was 580 ppm with respect to thehydrocarbon.

A third solution containing 23 wt % of ammonium heptamolybdate (AHM) wasmixed with a hydrocarbon stream (VGO1) containing Span 80T™ to form athird microemulsion wherein the hydrocarbon component was 95 wt % of thesecond microemulsion and Mo was 3580 ppm with respect to thehydrocarbon.

These separated emulsions were mixed in a processing unit to form atri-metallic catalyst and perform a catalytic reaction under conditionsshown in Table 5.

TABLE 5 Reaction Conditions Temperature (° C.) 390 Pressure (MPa) 10LHSV (h⁻¹) 0.5 H₂ flow (SCCM) 100

The resulting oil characterization is shown in Table 6 and shows theeffectiveness of the catalyst in reducing sulphur content andhydrocracking.

TABLE 6 % wt Cut (° C.)  0-273 28 273-380 38 380-450 18 450+ 16 S (% wt)0.27 API Gravity 14Particle Size Characterization

Various catalysts were evaluated to determine the particle sizedistribution of the catalysts using dynamic light scattering (DLS). DLSirradiates a liquid sample with light and observing time-dependentfluctuations in the scattered intensity using a suitable detector. Thesefluctuations arise from random thermal (Brownian) motion and thedistance between them is therefore constantly varying. Analysis of thetime dependence of the intensity fluctuation can yield the diffusioncoefficient of the particles and the hydrodynamic radius or diameter ofthe particles can be calculated.

DLS indicated general particle size ranges as follows:

-   -   bimetallic Ni—W—148 to 534 nanometers (nm)    -   Co—Mo—380 to 665 nm    -   tri-metallic Ni—W—Mo—380 to 665 nm

The measurements were checked using scanning electron microscopy (SEM).It is also understood that the foregoing size ranges are representativeonly and only refer generally to observed size ranges for specificcatalyst compositions. It is understood by those skilled in the art thatdifferent size ranges may be realized in accordance with the inventioneither within or outside the size range examples given above.

The above-described embodiments of the present invention are intended tobe examples only. Alterations, modifications and variations may beeffected to the particular embodiments by those of skill in the artwithout departing from the scope of the invention, which is definedsolely by the claims appended hereto.

1. A catalyst composition of the general formula:B_(x)M1_(y)M2_(z)O_((2 to 3)z)S_([(0.3 to 2)y+(0.5 to 4)x]) where B is agroup VIIIB non-noble metal and M1 and M2 are group VI B metals and0.05≦y/x≦15 and 1≦z/x≦14 and wherein the catalyst composition is anultradispersed suspension in a hydrocarbon solvent with a medianparticle diameter from 30 nm to 6000 nm.
 2. A catalyst composition as inclaim 1 wherein 0.2≦y/x≦6.
 3. A catalyst composition as in claim 1wherein z/x is 10≦z/x≦14.
 4. A catalyst composition as in claim 3wherein z/x is
 12. 5. A catalyst composition as in claim 3 wherein1≦z/x≦5.
 6. A catalyst composition as in claim 5 wherein z/x=3.
 7. Acatalyst composition as in claim 1 wherein the ultradispersed suspensionis characterized by a median particle diameter between 60 nm to 2500 nm.